1. Field of the Invention
The present invention relates to a rotational machine provided with a brake, such as a traction machine of an elevator.
2. Description of the Background Art
A known example of a rotational machine having a brake is a traction machine used in an elevator. Lubricant is used at bearings of a traction machine of this kind. If the lubricant leaks into a gap between the brake and a rotating portion of the machine with which the brake comes into contact, a braking force produced by the brake is considerably reduced. Conventionally, there are provided oil seals near the bearings. Taking into account the fact that the oil seals deteriorate as a result of long-term use, however, the oil seals employ a structure which more or less allows leakage of the lubricant in principle.
To overcome this leakage problem, Japanese Laid-open Patent Publication No. 2002-302356 discloses an arrangement in which an elevator is furnished with an oil leakage sensor located in a gearbox for detecting leakage of lubricant from a bearing portion of a traction machine. When the oil leakage sensor detects leakage of the lubricant, an equipment maintenance company is informed of this situation so that the company's servicing personnel can provide prompt servicing. According to the Publication, the oil leakage sensor includes a float switch held in a receptacle for detecting a liquid level. The float switch is activated when the leakage of the lubricant deposited in the receptacle reaches a specified amount.
According to the arrangement of the aforementioned Publication, it would be possible to inform the equipment maintenance company of the need for servicing so that the company's servicing personnel can promptly service the elevator when the oil leakage sensor has detected lubricant leakage caused by deterioration of an oil seal. It is however necessary to keep the elevator shut down while servicing work is being carried out, making it impossible to use the elevator for some time.
Another problem of this conventional arrangement is that, if the lubricant leaks in large quantities, it would instantly flow out and spread over a rotating portion of a traction mechanism with which a brake comes into contact, resulting in a reduction in braking force, for instance, although it might be possible to detect lubricant leakage with the oil leakage sensor.